Vanadium-columbium alloys



Limited States Patent .0

3,136,631 VANADIUM-COLUMBIUM ALLOYS Stanley T. Wlodek, Niagara Falls, N.Y., assignor to IYJniIIJn Carbide Corporation, a corporation of New No Drawing. Filed Apr. 27, 1960, Ser. No. 24,887

4 Claims. (Cl. 75-134) The present invention relates to vanadium-columbium alloys possessing exceptional high temperature strength and resistance to a variety of corrosive media and in addition possess resistance to atmospheric oxidation sufiicient to enable them to be fabricated at elevated temperatures by conventional techniques without the necessity of elaborate atmospheric controls.

It is an object of this invention to provide an alloy having excellent tensile, and stress-rupture strength atelevated temperature.

It is another object of this invention to provide an alloy having high resistance to corrosive media such as wet chlorine gas; and boiling sulfuric, nitric and hydrochloric acid.

It is a further object of this invention to provide an alloy having a superior strength-to-weight ratio.

It is still another object of this invention to provide an alloy of exceptional mechanical strength having in addition outstanding resistance to aqueous corrosive media and sufficient resistance to atmospheric corrosion, particularly air oxidation, with the result that high temperature fabrication can be performed thereon in air by conventional means.

These and other objects and advantages will become apparent from the following description.

The invention broadly consists of a new and improved high strength, corrosion resistant alloy containing from about 15 to 60 weight percent columbium up to 25 weight percent titanium; to 30 weight percent of at least one element of the group consisting of molybdenum, tantalum, tungsten and iron; 0 to 10 weight percent of at least one element of the group consisting of chromium, aluminum, cobalt, nickel, zirconium and hafnium; 0 to weight percent of at least one element of the group consisting of silicon, beryllium, and the lanthanides; less than 1 weight percent in the aggregate carbon, oxygen, and nitrogen; and the balance consisting essentially of vanadium, the vanadium comprising at least about 30 weight percent of the alloy and the sum of vanadium and c'olumbium to comprise at least about 50 weight percent of the alloy.

Patented June 9, 1964 The preferred alloy consists of 25 to 40 weight percent columbium; 5 to 15 weight percent titanium; 15 to 25 weight percent of at least one element of the group consisting of molybdenum, tanalum and tungsten when present; 0 to 5 weight percent of at least one element of the group consisting of chromium, aluminum, cobalt, nickel, zirconium and hafnium; 0 to 3 weight percent of at least one element of the group consisting of silicon, beryllium and the lanthanides, less than 1 weight percent in the aggregate of carbon, oxygen and nitrogen; and the balance consisting essentially of vanadium, the vanadium comprising at least about 40 weight percent of the alloy and the sum of vanadium and columbium to comprise at least about weight percent of the alloy.

The elements which are added to the binary columbiumvanadium system are classified in the following groups which are characterized by their degree of solubility inthe columbium-vanadium binary alloy and the following general characteristics commonly associated with their presence in this binary system.

HIGHLY SOLUBLE ELEMENTS Titanium additions increase oxidation resistance, improve corrosion resistance in aqueous oxidizing media and up to 7 weight percent titanium improves the mechanical properties of the alloy. Titanium also tends to stabilize vanadates.

Molybdenum, tantalum and tungsten additions are employed to impart corrosion resistance and to provide better mechanical properties.

INTERMEDIATELY SOLUBLE ELEMENTS The addition of chromium, aluminum, cobalt, nickel, zirconium, iron and hafnium will increase oxidation resistance of the binary columbium-vanadium system and since these elements differ in atomic size and lattice, they also tend to increase the tensile strength of the alloy. These elements also tend to reduce the amount of V 0 formed under oxidizing conditions.

LOW SOLUBILITY ELEMENTS Silicon, beryllium and the elements of the lanthanide series are strong oxide formers.

When one or more elements characterized by high solubility in the vanadium-columbium matrix, in particular, titanium, molybdenum, tantalum and tungsten are added, an increase in the resistance of the resulting alloy topure Table 1 RESULTS OF CORROSION TESTS ON VANADIUM ALLOYS As-east buttons] Corrosion rate, mils/year Composition, percent by weight Rm. Boiiing temp, 65% Bolling H01 Boiling H350 wet Ola N; V Cb Ti 5% 10% 15% 5% 10% 20% 30% 2 737 18 49 163 18 28 45 76 1 116 14 39 104 14 25 35 64 1 17 8 50 83 11 17 31 1 18 11 46 129 15 32 56 109 1 18 17 75 251 33 58 118 196 1 9 13 192 22 51 94 158 Diss 40 200+ 40 1..

Prior art alloys (nominal compositions, pereeut by wt.)

99+ii, 0.2 Pd 1 4-26 7 32 267 20 69 207 60 Ni, 30 Mo, 5 Fe, rem. Mn and Si 7 9 14 1 2 2 2 56 Ni, 16 Mo, 16 Cr, 5 W, 5 Fe,

rem. Mn and Si 1 332 21 33 304 Stainless Steel 10 oxygen at elevated temperatures is obtained as well as a corresponding increase in the resistance of said alloy to aqueous oxidizing media.

As an example illustrating the foregoing, reference is made to Table I which sets forth data on the corrosion behaviour in various aqueous media of the alloys of the present invention; and for comparison, pure vanadium, and select number of outstanding corrosion resistant alloys of the prior art are tabulated.

It may be seen from the foregoing table that alloys representative of this invention possess corrosion resistance comparable to, if not more superior than, the best corrosion resistant alloys available.

It has further been found that chromium, aluminum, cobalt, nickel, zirconium, hafnium or iron may be added to the alloy to augment the strength as well as enhance the oxidation resistance.

For examples illustrating the foregoing, reference may be had to the following Table II and Table III and Table IV. Table II sets forth data on the oxidation behaviour at elevated temperatures of the present alloys.

Table II OXIDATION RESISTANCE OF VANADIUM-COLUMBIUM ALLOYS Table III further illustrates the oxidation resistance of the alloys of the present invention by showing the rate of steady-state oxidation after 5.0 hours exposure to pure Table III OXIDATION RATES OF VANADIUM-GOLUMBIUM ALLOYS Rate of steady-state Composition, percent by wt. oxidation in pure oxygen (mgJcmJ/hr.)

V Cb Tl Other 700 0. 800 C. 900 C.

Table IV MECHANICAL PROPERTIES OF VANADIUM-COLUMBIUM ALLOYS Alloy composition weight percent Ultimate tenlsiletstrength in p.s. a

V Cb Ti Other 400 0. 700 C. 1000 C.

Prior art alloys Pure vanadium 52, 500 20, 000 7, 500 310 Stainless Steel 80, 000 50, 000 17, 000 40 Table V CREEP PROPERTIES OF V-Cb ALLOYS AT 700 C.

Minimum cregp rate (ln./ln.lhr.) or-- Alloy composition wt. percent 75,000 p.s.i. 90,000 p.s.i. 100,000 11.5.1.

V-40 Ob 1. 05X10- 60 V-40 Cb-iO 'Ii 1 0 X10 50 49 V-40 Cb-10 Ti-1 Si- 1 Xl0 oxygen. worked.

Table VI EFFECT OF PROCESSING VARIABLES ON MECHANICAL PROPERTIES Alloy composition, Annealed R.T., 0.2% 700 0., 0.2% 1000 C., 0.2% 1200" 0., 0.2%

wt.pereent swaged condition Temp., Time, U.T.S., Y.S., E, U.T.S., Y.s., E, U.T.S., Y.s., E, U.'1.S., Y.S., E, V Cb Ti C. hr. p.s.i. p.s.i. perp.s.i. p.s.i. perp.s.i. p.s.i perp.s.i. p.s.i per- X10- 10- cent X10" X10 cent XlO- X10" cent X10- X10 cent 30%QW Brit le failure 128.6 109.6 5.2 %1100C Brittle failure 130.2 112.0 6.0 70.1 63.7 89 23.2 22.4 43.6 50% 1100C 1100 0. 5 50% 1100C 1200 0. 5 1100C 1300 0. 5 50% 1000C 1000 0. 5 50% 1000C 1100 0.5 50% 1000C- 1300 0.5 40% C.W

1 All tests performed at 0.02- see. strain rate.

As may be observed from the foregoing Table II the present alloys exhibit remarkable superiority in oxidation resistance at elevated temperatures over pure vanadium. It is further noted that the columbium-titaniumvanadium alloy shows anoutstanding increase in oxidation resistance. The resistance of the 45 weight percent vanadium, 40 weight percent columbium, 10 weight percent titanium and 5 weight percent silicon alloy is also notable.

It may be noted from Table IV that the binary and its modifications surpass both pure vanadium and type 310 stainless steel in tensile strength at elevated temperatures. Particularly noteworthy is the exceptional strength of the alloys containing 10 weight percent titanium and 1 weight percent silicon at 700 C.

The addition of silicon, beryllium, barium, and the lanthanides, increases the resistance of the resulting alloy to oxidation at elevated temperatures. Examples illustrating this may be had by reference to the aforementioned Table II. It may be further observed that additions of these elements appreciably augment the mechanical strength. This fact is amply demonstrated in both Table IV and Table V. Table VIl sets forth data on the stress rupture properties of the subject alloys. Two commercial alloys of outstanding high temperature strength and type 310 stainless steel are included for purposes of comparison.

Table VII STRESS-RUPIURE PROPERTIES OF VANADIUM-COLUM- BIUM ALLOYS UNDER HELIUM ATMOSPHERE Alloy composition, weight percent Stress for ih0ur1iie at 700C.

Prior art alloys nominal composition by weight percent 20 Cr, 12 Co, 10 Mo, 3 Ti, 1.5 A1, Rem.

20 Cr, 20 Co, 5 Mo, 4 Fe, 3 Ti, 3 Al, Rem.

310 Stainless Steel 0. 28 20, 000 71, 500

The evidence of Table VII serves to demonstrate the outstanding strength and particularly the strength-toweight ratio of the alloys of this invention. On this basis it is possible to conclude that said alloys have stressrupture properties, on a density basis, well in excess of those of any other known material at 700 C.

In all the foregoing tables, the alloys of the present invention noted therein contain less than about 1 weight percent in the aggregate of carbon, oxygen and nitrogen. The alloys of the present invention can be prepared by any consumable or nonconsumable arc melting techniques or any powder metallurgical process. The alloys can, of course, be processed also by forging, rolling, and standard extrusion. Although a primary reduction at elevated temperature is recommended, subsequent fabrication can be performed at temperatures as low as room temperature.

One of the most important novel aspects of these alloys is that they can be hot worked without the necessity of protective cover either from special coating or blanket of inert gas. This feature greatly simplifies and lessens the cost of fabrication.

From the foregoing it will be evident that alloys of the present invention exhibit excellent mechanical strength at elevated temperatures and in addition exhibit outstanding corrosion resistance to both aqueous and gaseous environments.

These alloys are particularly useful where extreme temperatures and operating conditions are met such as, for instance, those conditions which are associated with propulsion systems and nuclear reactors.

I claim:

1. An alloy comprising 25 to 40 weight percent columbium 3 to 15 weight percent titanium, 15 to 25 weight percent of at least one element selected from the group consisting of molybdenum, tantalum, tungsten and iron; up to 5 weight percent of at least one element selected from the group consisting of chromium, aluminum, cobalt, nickel, zirconium and hafnium; up to 3 weight percent of at least one element selected from the group consisting of silicon, beryllium, and the lanthanides; not more than 1 weight percent in the aggregate of carbon, oxygen and nitrogen; and the remainder vanadium in at least 40 weight percent, wherein the sum of said vanadium and said columbium comprises at least 65 weight percent in the aggregate.

2. An alloy consisting essentially of 25 to 40 weight percent columbium, 3 to 15 weight percent titanium; up to 5 weight percent of at least one element selected from the group consisting of chromium and aluminum; up to 3 weight percent silicon, less than about 1 weight percent in the aggregate of carbon, oxygen and nitrogen, and the remainder vanadium in at least 40 weight percent.

3. An alloy consisting of from 3 to 15% titanium, '25- 40% columbium, balance vanadium.

4. An alloy comprising 40 weight percent columbium; 5 weight percent chromium; about weight percent vanadium and less than about 1 weight percent in the aggregate of carbon, nitrogen and oxygen. 

1. AN ALLOY COMPRISING 25 TO 40 WEIGHT PERCENT COLUMBIUM 3 TO 15 WEIGHT PERCENT TITANIUM, 15 TO 25 WEIGHT PERCENT OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM, TANTALUM, TUNGSTEN AND IRON; UP TO 5 WEIGHT PERCENT OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, ALUMINUM, COBALT, NICKEL, ZIRCONIUM AND HAFNIUM; UP TO 3 WEIGHT PERCENT OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF SILICON, BERYLLIUM, AND THE LANTHANIDES; NOT MORE THAN 1 WEIGHT PERCENT IN THE AGGREGATE OF CARBON, OXYGEN AND NITROGEN; AND THE REMAINDER VANADIUM IN AT LEAST 40 WEIGHT PERCENT, WHEREIN THE SUM OF SAID VANADIUM AND SAID COLUMBIUM COMPRISES AT LEAST 65 WEIGHT PERCENT IN THE AGGREGATE. 